Besarab A, DeGuzman A, Swanson J W
J Clin Pathol. 1981 Dec;34(12):1361-7. doi: 10.1136/jcp.34.12.1361.
In vivo equilibrium dialysis studies were performed to define further the characteristics of calcium binding to bovine albumin. The concentration range for albumin (1 to 9 g/dl) as well as ultrafilterable calcium (0.5 to 2.5 mM) studied encompassed those that might be ordinarily encountered in most clinical situations. Major differences in the regressions of total calcium on ultrafilterable calcium occurred at albumin concentrations of 1, 2, and 9 g/dl but only small differences at albumin concentrations between 3, 5 and 7 g/dl. When albumin concentration was kept constant, the amount of calcium bound to albumin varied directly with ultrafilterable calcium. At any constant ultrafilterable calcium concentration albumin bound calcium varied inversely with the albumin concentrations when albumin was greater than 3 g/dl. Analysis of the data to determine association constants and molar calcium to albumin binding ratios showed that both parameters were dependent on the absolute albumin concentrations. Our results indicate that calcium binding to albumin is a complex process characterised by multiple binding sites whose affinity and binding capacity are variable. These properties suggest that correction of total serum calcium using clinical formulations with fixed calcium to albumin binding ratios may be inappropriate, particularly in hypoalbuminaemic states.
进行了体内平衡透析研究，以进一步确定钙与牛血清白蛋白结合的特性。所研究的白蛋白浓度范围（1至9 g/dl）以及可超滤钙浓度范围（0.5至2.5 mM）涵盖了大多数临床情况下可能遇到的浓度。总钙对可超滤钙的回归分析在白蛋白浓度为1、2和9 g/dl时存在主要差异，但在白蛋白浓度为3、5和7 g/dl之间仅有微小差异。当白蛋白浓度保持恒定时，与白蛋白结合的钙量随可超滤钙浓度直接变化。在任何恒定的可超滤钙浓度下，当白蛋白浓度大于3 g/dl时，白蛋白结合钙量与白蛋白浓度呈反比。对数据进行分析以确定结合常数以及钙与白蛋白的摩尔结合比，结果表明这两个参数均取决于白蛋白的绝对浓度。我们的结果表明，钙与白蛋白的结合是一个复杂的过程，其特征在于多个结合位点，这些位点的亲和力和结合能力是可变的。这些特性表明，使用具有固定钙与白蛋白结合比的临床公式来校正总血清钙可能并不合适，尤其是在低白蛋白血症状态下。
